Author: Rani, Varsha
Presence of vessels in the ocean has a significant impact on northern resident killer whales (NRKWs). In this study, we investigated the effects of physical disturbance caused by vessels on NRKWs' beach rubbing behaviour, a cultural behaviour of importance to these whales. We hypothesized that the presence of vessels would deter NRKWs from beach rubbing, but we also investigated the influence of tide height and vessel distance from the rubbing beaches on this behaviour. From July through September in 2020 and 2021, our study was conducted in and adjacent to the Robson Bight (Michael Bigg) Ecological Reserve (RBMBER), a marine reserve in Johnstone Strait, British Columbia (BC) where the rubbing beaches exist. The data were collected from a land-based platform and analysed using GAMM. We found that NRKWs preferred the beaches inside RBMBER, and proximity of vessels to NRKWs at the rubbing beach outside RBMBER affects their decision to rub, as the probability of beach rubbing increases as the distance between NRKWs and vessels increases. Tide height influences beach rubbing only at the beaches inside RBMBER. Given the results, it is evident that vessel presence and their proximity to whales in critical habitats need to be addressed and the existing guidelines need amendments.
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Thesis advisor: Joy, Ruth
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